It is often necessary in tooth restoration to combine radically curing dental materials, in particular formulations which contain inorganic fillers in a radically curable organic matrix (so-called composites), with other metal- or mineral-based dental restoration materials. In particular, in the case of restoration materials, a distinction is drawn between the following material types: noble metals (e.g. gold, platinum, palladium, silver and their alloys), base metals (e.g. chromium, nickel, molybdenum, titanium and their alloys), siliceous ceramics (e.g. feldspar, quartz, leucite-based ceramics or glass ceramic) or non-siliceous ceramics (e.g. yttrium-stabilized zirconium oxide, aluminium oxide, glass-infiltrated aluminium oxide). Adhesion promoters (primers) are used to improve the adhesion between the aforementioned restoration materials and the radically curing dental material. Primers known to date for adhesively securing dental restoration materials are normally suitable in each case for only one of the named material types and do not offer clinically useful adhesion to other substrates.
DE 10 2005 002 750 A1 discloses a primer for dental noble metal alloys that contains special disulphides substituted with polymerizable groups.
EP 0 224 319 A1 describes a primer composition for improving adhesion to various ceramic materials that contains a silane which can be hydrolyzed to an organofunctional silanol. Although an improvement in adhesion to metal materials is also demonstrated in EP 0 224 319 A1, it transpires in practice that the described primers act only on siliceous ceramics.
The subject of JP 2601254 B2 is a dental primer for ceramics and metal which contains the combination of an organofunctional silane with special (meth)acryloyloxy-functional phosphoric acid monoesters. JP 2593850 B2 describes a dental adhesive composition which contains inter alia an organofunctional silane and an acid organic phosphorus compound with a radically polymerizable double bond. The composition is said to make possible bonding to both metals and ceramics. However, on noble metal surfaces, such as gold, no chemical bonding is effected with the two compositions named above and thus there can be no durable bond between metal and a radically curing dental material with these compositions, in particular because of the different coefficients of thermal expansion of the materials to be joined.
WO 2008/053990 also discloses a dental adhesive composition which contains the combination of a silane coupling agent with special (meth)acryloyloxy-functional phosphoric acid monoesters. The composition is said to display a good adhesion both to dental ceramics and to organic composites which contain inorganic materials.
The scientific literature reports that specific adhesion monomers are especially suitable for special types of metal or ceramic (see for example Kern M, Wegner M S, “Bonding to Zirconia Ceramic: Adhesion Methods and Their Durability”, Dent Mater 1998, 14; 64-71; Yoshida K, Kamada K, Atsuta M, “Shear Bond Strength of a New Resin Bonding System to Different Ceramic Restorations”, Int. J. Prosthodont 2007, 20; 417-418).
However, a disadvantage of using substrate-specific primer systems is that because of the variety of substrate types a corresponding number of primers becomes necessary. However, in the case of clinical use, as the number of substrate-specific primer systems increases, so does the danger of confusion and thus also the risk of clinical failure. In addition, a precise application of a substrate-specific primer is clinically not possible in many cases, such as for example when repairing a fractured ceramic veneer, since there is more than one substrate directly next to each other in a narrow space.
Accordingly the object of the invention is to provide a universal adhesion promoter that is characterized by a good bonding effect between a radically curing dental material, in particular a composite, and many other dental restoration materials. A good bonding effect is also to be preserved after an alternating thermal load.